Progesterone altered amino acid accumulation by human endometrium in vitro |
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Authors: | S S Shapiro M H Johnson |
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Affiliation: | Department of Obstetrics and Gynecology, University of Wisconsin, Madison 53705. |
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Abstract: | When human endometrium is exposed to progesterone, the rate of amino acid incorporation into its protein pool is altered. Accumulation into specific proteins has been evaluated by one-dimensional polyacrylamide gel electrophoresis. Comparison of steroid-exposed and nonexposed tissue has revealed a change in the rate of radiolabeled amino acid uptake into a few stained protein bands. To further characterize the effect of progesterone on endometrial protein metabolism, we have examined the one-dimensional electrophoretic band that undergoes the greatest change in leucine accumulation using two-dimensional gel and monoclonal antibody technologies. The band of interest results from altered amino acid uptake into a single protein spot on two-dimensional gels. This particular protein has an approximate size of 50 kDa and pI of 5.8. It exists in a monomeric form under nondenaturing conditions. During organ culture of proliferative endometrium exposed to 0.1 micrograms/ml progesterone, there is a sixfold increase in the rate of methionine uptake into this protein. The rate of amino acid accumulation is maximal after 24 h of culture in medium containing progesterone. Partial purification provided a product enriched 120-fold for this specific protein and facilitated development of a monoclonal antibody that was used to identify the protein in several human tissues besides endometrium. Antibody-antigen complex could not be detected in medium from secretory endometrium, suggesting that this protein resides in the cytosol without being secreted by the tissue. |
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